Automatic electric parking brake



United States Patent Leroy Taber 1205 S. 76 E. Ave., Tulsa, 74112; JamesW. Dillard; 346 S. Oak. Ponca City.

[72] Inventors Oklahoma 74601 [21] Appl No 730,183 [221 Filed May 17.1968 [45] Patented Nov. 10, 1970 [54] AUTOMATIC ELECTRIC PARKING BRAKE[56] References Cited UNITED STATES PATENTS 2,251,521 8/1941 McIntyre eta1 188/162 2,933,159 4/1960 Steibinger l. l88/162X Primary I:xaminer-Duane A. Reger Attorney Dunlap, Laney. Hessin & Dougherty ABSTRACT: Anautomatic electric parking brake system which includes an electricmotordrivingly connected through speed reduction gearing to a threadedshaft forming a portion of a movable carriage assembly The carriageassembly carries a pair of stop elements which are positioned to contactstationary limit switches mounted adjacent the carriage. with such limitswitches being interposed in electrical circuitry connected to theelectric motor and adapted to turn the motor in one of two directions ofrotation when the circuit through one or the other of the limit switchesis closed. The carriage is connected through a lost motion assembly tothe parking or emergency brake of an automobile \0 that this brake isapplied when the carriage moves in one direction. and released when thecarriage moves in the opposite direction. The electrical circuitry tothe electric motor 15 wired to include the ignition switch of theautomobile and suitable relays, such that when the ignition switch isturned to the ON" position, the motor will be energized to drive thecarriage in one direction, thereby releasing the emergency brake andultimately striking one of the limit switches to open the electricalcircuit to the motor, and so that when the ignition switch is turned tothe OFF" position electrical circuitry will be completed to the motor to-drive it in a different direction to move the carriage in a directionto apply the brake. Setting and releasing of the brake is thusaccomplished automatically upon actuation of the ignition switch of theautomobile.

Pdtented Not 10, 1970 Sheet 1 '2 J S f QN Q l wm 8 3%. E ma L INVIZNTOKQ6. Q D0 W MW 7 Y 0% W MM I 1 AUTOMATIC ELECTRIC PARKING BRAKE BACKGROUNDOF THE INVENTION 1 Field of the Invention I This invention relates toautomaticemergency or parking brake systems for automobiles which areelectrically actuated upon opening orclosing the ignition switch of theautomobile.

ing the normal and usual operation of the automobile, to automaticallyapply an emergency or parking-brake when certain operations'conducted inthe normal course of driving and operating the automobile are carriedout. In some of these instances, automatic-actuation of mechanismnecessary to set or apply the brake is accomplished by the use of thevacuum developed by the internal combustion engine of the automo bile,and in others, application of the brake is accomplished byeleetricalenergy. In either event, the systems which have been thus farproposed have generally been complicated in structure and, insome cases,have interfered with the regular braking system of the vehicle, or haveexcluded the option available to the operator. of a manually appliedbrake which is conventional equipment on mostautomobiies.

BRIEF DESCRIPTION OF THE PRESENT INVENTION The presentinvention may bebroadly described as comprising a reversible electric motor, atrackway,a carriage movable in reciprocation on the trackway, and means drivinglyconnecting the motor to the carriage. The carriage has one of its endsconnected through 'a resilient member to alost motion assembly which inturn is connected to the cable secured to the emergency brakes locatedat the rear wheels of the automobile. The lost motion assembly is alsointerconnected between the manual hand or footcontrol for theemergencybrake and the brake cable so that the automatic electrical brakecontrolsystem and the manual control system can be utilizedindependently of each other.

Electrical circuitry including a pair of limit switches, the reversiblemotor, and the automobile ignition switch is connected to a source ofelectrical current. The limit switches are preferably mounted onthetrackway at spaced points so that stop elenientsmounted on the carriagewill contact the limit switches in alternating sequence as the. carriageis reciprocated along the trackway in opposite directions. The

circuitry is constructed so that closing the ignition switch (turningitONto start and run the engine) will energize'the reversiblemotor-sufficiently to drive thecarriage toone of its limits of travel,and in doing so, will act'through theflost motion assembly to releasethcbrake, When-the ignition switch is turnedOFF, a-different circuit ismade through the motor to drive it in the'reversedirection,and-reverse-the direction of travelof the carriageuntil itstrikesanother limit switch to deenergizethe motor. This movement ofthecarriage tensions the emergency brake cable to set the emergency brakes.

In a preferred embodiment of the invention, the electrical circuitryfurther includes switching means which permits the described automaticcontrolto be utilized, or as a second option, permits'immediateelectrical application of the brakes at any time to be effected.

, Fromthe foregoingdescription of the invention, it will be perceivedthat a major object of the invention is to provide an automaticemergency brake system'which functions to automatically applytheemergency or parking brakes when the ignition switch is turned to an OFFstatus to render the vehicle inoperative, and to automatically releasethe emergency or parking brakes when the ignition-switch is turnedto anON position.

Another object of ,the invention is to provide an automatic,electrically powered emergency and parking brake system whichdoesnotrender inoperative or in any way interfere with the conventional"manual emergency and parking brake system,

An additional object of the invention is to provide an electricallyactuated emergency brake system which can be easily accommodated to theconventional emergency braking system of existing automobiles.

A further object of the invention is to provide an electrically actuatedbraking system which may be quickly made either automatically actuatedin response to the turning on and off of the ignition switch of anautomobile, or alternately, may be actuated to apply the emergencybrakes at any time desired. re-

gardless of the status of the ignition switch.

Yet another object of the invention is to provide an automatic,electrically actuated parking brake system which is relatively simpleand inexpensive in construction, yet is characterized in having a longand trouble-free operating life.

Additional objects and advantages will become apparent as the followingdetailed description of the invention is read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic plan view ofthe mechanical portion of the invention.

FIG. 2 is a view in elevation of the channel trackway and movablecarriage utilized in the invention.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2.

FIG. 4 is a side elevation view of a lost motion assembly utilized inthe invention.

FIG. 5 is a view similar to FIG. 4, but illustrating an operativeposition of the lost motion assembly different from that iilustrated inFIG. 4.

FIG. 6 is a plan view of the lost motion assembly in the status itoccupies in FIG.4.

FIG. 7 is a sectional viewtaken along line 7-7 of FIG. 4.-

FIG. 8 is electrical circuitry utilized in one embodiment of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Referringinitially to FIG. 1 of the drawings, the automatic electric parkingbrake of the invention includes a reversible motor 10 which is drivinglyconnected through a flexible drive cable l2 to reduction gearing locatedin a housing 14. The reduction gearing in the housing I4 drivinglyengages a threaded shaft I6 which is passed through the housing so thatthe flexible cable can drive the threaded shaft l6 in reciprocationrelative'to the housing. The housing 14 is secured to an elongatedchannel trackway designated generally by reference numeral 18. Thechannel trackway I8 has a flat bottom plate 20 and .a pair of turnedover, semicircular edge portions 22 and is open at its opposite ends.The channel trackway 18 carries at its opposite ends, a pair of mountingstraps 24 which are apertured so that the channel 18 can be secured toany suita- 1 ble portion of an automobile by means of bolts 26.

Slidably mounted for longitudinal movement in the channel trackway I8 isa carriage designated generally by reference to move smoothly in thechannel trackway 18. Other suitable materials having a low coefficientof friction may be employed in place of the Teflon runners.

Secured to the base plate 30 by means of screws, bolts, welding, orother suitable arrangement, is a pair of U-shaped brackets 34 and 35.Each of the U-shaped brackets 34 and 35 has secured to one of the legsthereof, an outwardly extending supporting element 38 which ispositioned above the turned over edge portion 22 of the channel 18. Eachof the supporting members 38. carries an adjustable stop member which,in the illustrated embodiment of the invention, is an adjusting screw40. It will-he noted that the position of the head of each adjustingscrew 40 with respect to its supporting member 38 can be varied byscrewing the adjusting screw varying distances into the supportingmember. The head of each of the adjusting screws 40 faces in the generaldirection of the housing 14 of the reduction gearing located at aboutthe center of the carriage 28 for a purpose which will hereinafterbecome apparent. It will also be noted in referring to FIGS. 2 and 3that the supporting members 38 are vertically offset with respect toeach other.

Disposed at a location in approximate alignment with the housing of thereduction gearing, and at about the center of the channel trackway 18,is a switch mounting bracket 44 which may be mounted in the illustratedposition by welding or otherwise suitably securing its lower end to oneof the turned over edge portions 22 of the base plate 20 of the channeltrackway 18. The switch mounting bracket 44 includes a pair of retainerrings 46 in which is mounted a pair of limit switches. These limitswitches will hereinafter be referred to as an applying limit switch anda releasing limit switch, and will be designated by reference numerals48 and 50, respectively. The applying limit switch 48 and the releasinglimit switch 50, respectively, are connected with the reversible motorin electrical circuitry which will hereinafter be described in greaterdetail.

Secured to the bight portion of the U-shaped bracket 35 is a tail plate52 which extends toward the end of the channel trackway I8 and isapertured to accommodate a pivot pin 54. The pivot pin 54 is passedthrough the aperture in the tail plate 52 and through an L-plate 56forming a portion of an adjusting link assembly designated generally byreference numeral 58. The adjusting link assembly 58 further includes abolt 60 having a threaded shank portion which is threaded through locknuts 62 disposed on opposite sides of one of the legs of the L- plate 56as best illustrated in FIG. I. At one end of the threaded bolt 60, thebolt carries an eye to which is connected one end of a relatively largeexpansion spring 64. The second end of the expansion spring 64 isconnected to the emergency or parking brake actuating element 66 forminga portion of a lost motion assembly designated generally by referencenumeral 68.

The lost motion assembly 68 includes, in addition to the automatic brakeactuating element 66, a manual brake actuating element 70 and a centralguide member 72. The automatic brake actuating element 66 and the manualbrake actuating element 70 are each ofC-shaped cross-sectionalconfiguration as best illustrated in FIG. 7, and are each provided witha centrally located, elongated slot 74 as shown in FIG. 6. Each of thebrake actuating elements 66 and 70 also includes apertured nose pieces76 and 78 located at each end thereof.

The central guide member 72 is of generally H-shaped cross-sectionalconfiguration and has outwardly extending, substantially parallel flangepairs 72a, 72b, 72c, and 72d which define elongated slots or groovesreceiving the in-turned flanges of the automatic brake actuating element66 and the manual brake actuating element 70. A retainer bolt 80 isextended through the central guide member 72 relatively near to its endopposite the end of the lost motion assembly 68 which is connected tothe expansion spring 64. The bolt 80 is also extended through theelongated slots 74 which are located in both the automatic brakeactuating element 66 and the manual brake actuating element 70. Withthis arrangement, both of the brake actuating elements 66 and 70 arefree to slide longitudinally with respect to the guide member 72 untilthe bolt 80 has moved to one end or the other of the slot 74 in therespective actuating elements.

The manual brake actuating element 70 has its end most remote from thebolt 80 connected to one end ofa pull rod 84 which is secured at itsopposite end (not visible) to a conventional mechanical linkage whichinterconnects the pull rod to the usual hand or foot emergency brakeelement adapted for manual actuation by the driver of the automobile. Attheir ends opposite the ends connected to the expansion spring 64 andthe rod 84, respectively, the automatic brake actuating element 66 andthe manual brake actuating element 70 have their respective aperturednose pieces 78 connected to relatively small retraction springs 86 whichare connected by any suitable means to the frame 88 .of the automobilein the manner illustrated in FIG. 1. At the same end of the lost motionassembly 68, a projecting flange 90 of the central guide member 72 isconnected to a rear adjusting link assembly 58 of the type which hasbeen hereinbefore described. The adjusting link assembly 58 thusincludes an L-plate 56 and a threaded bolt 60. The L-plate 56 ispreferably secured to the frame through an intervening, relativelysmall, retraction spring 92.

Extended through the eye of the threaded bolt 60 is a flexible brakecable 94 which is extended rearwardly along the automobile (not shown)and connected at its opposite ends to the emergency or parking brakes ofthe automobile in a conventional manner. In some instances, it may bedesirable to connect the rear adjusting link 58 to a lever bar providedin some automobile models for the purpose of applying leverage to thebrake cable 94. Where this arrangement is in use, the automatic electricparking brake system of the invention can easily be adapted toconnection to the lever bar.

The electrical circuitry employed in the present invention isillustrated in FIG. 8 of the drawings.

It will be noted in referring to this FIG. that, as previouslyindicated, the electrical circuitry includes the reversible motor 10,the applying limit switch 48, and the releasing limit switch 50. Alsoincluded in the electrical circuitry is a conventional automobileignition switch having ON, OFF, and START positions as illustrated.There is optionally provided in the circuitry, a two-position switch 102for placing the emergency brake system in automatic operation, or formanually applying the emergency brake through the use of this switch ina manner which will be hereinafter described. The circuitry furtherincludes a relay 104 which is connected in parallel with the releasinglimit switch 50 and which actuates a switch 106 when the relay isenergized. A battery 108 provides a source ofelectrical current tooperate the system, and the battery, reversible motor 10, and the coilof the relay 104 are grounded in the manner illustrated in FIG. 8.

OPERATION The operation ofthe automatic electric parking brake of theinvention will be described from the standpoint of manipulation by thedriver ofthe automobile ofthe switch controls provided on the dashboardof the vehicle. Let it be assumed that the emergency or parking brake ofthe vehicle is in a released status during driving of the automobile,and it is desired to park or terminate operation of the vehicle. At thistime, the driver of the automobile first turns the ignition switch 100to the OFF position as illustrated in FIG. 8. When the switch is in thisposition, an electrical circuit is made from the battery, through theignition switch and through the coil of the relay 104 to ground. Thisstatus then results in the switch 106 being closed by the relay 104, anda circuit being made through the normally closed brake applying limitswitch 48 to the reversible motor through the switch 106. 4

The circuit is completed to ground, and the reversible motor isenergized to drive the flexible cable 12 in rotation. The flexible cablein turn drives the reduction gearing located in the housing 14 in adirection to cause the threaded shaft 16 to be reciprocated through thishousing in a downward direction in the diagrammatic illustration of FIG.8, or toward the left as the shaft 16 is viewed in FIG. 1. Movement ofthe threaded shaft 16 toward the left in FIG. I also carries with it thecarriage 28 so that the adjusting screw 40 moves toward the applyinglimit switch 48. The reversible motor 10 continues to drive the threadedshaft 16 in the direction of the brake applying limit switch 48 untilthis limit switch is contacted and opened by the biasing force exertedby the adjusting screw 40.

As the carriage 28 moves toward the left as viewed in FIG. 1, it carrieswith it the tail plate 52 and the adjusting link assembly 58 which ispivotally connected to the tail plate through the L-plate 56. TheL-plate 56 is positioned so that it may move between the up turned sideedges 22 of the trackway channel 18 and movement of the carriage 28 inthe described direction will bring the L-plate 56 over the bottom plate20 of the channel trackway. Movement of the adjusting link assembly 58toward the channel trackway 18 tensions the expansion spring 64 with theresult that a pull is applied to the automatic brake actuating element66 of the lost motion assembly 68. I

As the automatic-brake actuating element 66 of the lost motion assembly68 is reciprocated toward the channel trackway 18, it necessarilycarries with it the central guide member 72, since the bolt 80' islimited in its movement withrespect to both the automatic brakeactuating element 66 and the central guide member 72 by its contact withthe end of the elongated slot74 in the automatic brake actuatingelement. The central guide member 72 is ableto slide longitudinally withrespect to the brake actuating element 70, and the retraction spring 86connected to the latter element retains it in the position illustratedin FIG. 5. The lower end of the bolt 80 slides along the slot 74provided in the manual brake actuating element 70,

i and the flat leg of the L-plate 56 is able to move between the facing,in turned flanges of the manual brake actuating element as it followsthe central guide member 72.

The function of the expansion spring 64 in the assembly is to preventthe severance of the brake cable 94 or stalling out of the reversiblemotor 10. Adjustments of the amount of force applied by the assemblythrough the brake cable 94 to the emergency brakes at the rear of thevehicle can beeffected by adjusting the threaded bolt 60 in its relationto the L-plate 56 and lock nuts 62.

Now let it be assumed that the emergency or parking brake is in anapplied or set status as, has been described above, and it is desired tostart the vehicle, release the emergency brake, and proceed with normaldriving operations. At this time, the driver of the automobile firstturns the ignition switch to the START and then to the ON position. Whenthe ignition switch is in the ON position and the switch is positionedfor AUTO- MATIC operation, a circuit is made from the battery 108through the switches 100 and 102; and through the normally closedreleasing. limit switch50 to the reversible motor where the circuit toground is completed. This will energize the reversible motor so as todrive the flexible drive cable 12 in a direction such that the threadedshaft 16 is moved in a direction to move the head of theadjustable-screw 40 carried on the bracket 34 toward the releasinglimitswitch 50. This entails a movement of the carriage 28 to the right as itis motion of the threaded shaft 16 and the carriage 28 is also ter- Iminated. v

When the threaded shaft 16 and the carriage 28 to which it is connectedhave moved to this position, the tail plate 52 connected to the baseplate 30 of the carriage has been moved by the moving carriage totheright as it is viewed in FIG. 1 to re lieve the tension in theexpansion spring 64. This permits the retraction spring 86 to return theautomatic brake actuating element 66 to its position of alignment withthe central guide member 72 and the manual brake actuating element 70.Simultaneously, the retraction spring 92 connected to the adjusting linkassembly 58 which is secured to the rear endofthe central guide member72, coupled with the acting tension in the brake cable 94, retracts thecentral guide member 72 to its position of alignment with the automaticbrake actuating element 66 and the manual brake actuating element 70.The

brakes are thus released and they remain released as long as It willperhaps be apparent from the foregoing description that an alternatemode of operation of the emergency parking brake is always availableusing the system as thus far described. Thus, the usual manual settingor application of the emergency or parking brake can be effected throughthe conventional hand lever or foot brake provided for this purpose dueto the inclusion in the system of a lost motion assembly 68. Thus, whenthe conventional hand brake or foot pedal actuator is operated by thedriver of the automobile, pull is applied through the rod 84 to themanual brake actuating element 70. The manual brake actuating element 70can then more forward without disturbance of the automatic brakeactuating element 66 due to the construction of the lost motion assembly68. As the manual brake actuating element 70 is pulled forward, itcarries with it the central guide member 72. The central guide member 72can slide relative to the automatic brake actuating element 66 by reasonof its grooved structure, and the automatic brake actuating ,element 66is retained in its inoperative or released position by the bias exertedby its associated retraction spring 86. As the central guide member 72moves forward, it acts through the adjustable link assembly 58 totension the brake cable 94 in the manner hereinbefore described.

Another optional feature of the present invention which is included inthe preferred embodiment of the circuitry used to operate the brakingsystem of the invention is the two-position AUTOMATIC-MANUAL switch 102depicted in FIG. 8. When this switch is positioned in the automaticposition and the ignition switch is turned on, the same action as hasbeen described will occur, and when the ignition switch is turned off,the emergency brake will be automatically applied, also as hereinbeforediscussed. There may be occasions, however,

when it is desired to apply the emergency brake, even though i theignition switch is at that time on and in automatic operation. Theemergency brake would not be applied on such occasions.

To then apply the emergency brake, the switch 102 is moved to the MANUALposition, and in this position, a cir-,

cuit is immediately made through the coil of the relay 104 to ground.This closes the switch 106 in the manner hereinbefore described. Withclosure of the switch 106, a circuit is made.

through the reversible motor 10 to ground. The reversible motor 10 isthus drivenin a direction such that the shaft 16 is moved .in a brakeapplying direction, that is, to the left as viewed in FIG. 1 of thedrawings. This action will move the entire carriage 28 to the left,tensioning the expansion spring 64 and drawing the automatic brakeactuating element 68 toward the channelled trackway l8 and carriage 28.The central guide member 72 will move with the automatic brake actuatingelement 66, and the brake cable 94 will be tensioned to apply theemergency brakes.

From the description of the switch 102 in the electrical circuitry, itwill be perceived that this switch enables the opera tor to constantlyhave available, the option of whether to maintain the electricallyactuated brake system in automatic operation, or to use it for quicklyand easily applying the should be recognized that various changes andinnovations in the described structure can be effected without departurefrom the basic principles underlying the invention. All modificationsand changes of this type are therefore deemed to be circumscribed by thespirit and scope of the invention except as the same may be necessarilylimited by the appended claims or reasonable equivalents thereof.

I claim: 6

1. An automatic electric parking brake system comprising:

a reversible motor;

a carriage drivingly connected to said reversible motor forreciprocating movement in response thereto;

a trackway movably supporting said carriage and adapted for securementto an automobile;

a lost motion assembly comprising an automatic brake actuating elementflexibly connected to said carriage for following the movements of saidcarriage;

a manual brake actuating element;

a central guide member slidably positioned between and interconnectingsaid automatic brake actuating element and manual brake actuatingelement; and

means for moving said central guide member with either one of said brakeactuating elements relative to the other brake actuating element whensaid one brake actuating element is reciprocated in one direction;

means connected to said manual brake actuating element for connectingsaid manual brake element to a manual brake applying device;

flexible means secured to said central guide member and adapted forconnecting said central guide member to a brake;

a pair of spaced limit switches;

means mounted on said carriage and positioned for alternately contactingsaid limit switches during the reciprocating movement of said carriage;

an automobileignition switch;

a battery; and

electrical circuitry interconnecting said reversible motor, limitswitches, ignition switch and battery for driving said motor in onedirection when said ignition switch is turned to an ON position and oneof said limit switches is closed, and for driving said reversible motorin a second direction when said ignition switch is turned to an OFFposition and the other ofsaid limit switches is closed.

2. An automatic electric parking brake system as defined in claim 1 andfurther characterized to include:

a flexible drive cable drivingly connected to said reversible motor;

gearing connected to said flexible drive cable; and I a threaded shaftsecured to said carriage and engaged by said gearing.

3. An automatic electric parking brake system as defined in claim 1wherein said trackway comprises:

a flat bottom plate;

turned over edge portions engaging and guiding said carriage; and

means for securing said bottom plate and edge portions to an automobile.

4. An automatic electric parking brake system as defined in claim 1wherein said carriage comprises:

an elongated base plate movably mounted in said trackway;

first mounting means secured to said base plate;

second mounting means secured to said base plate and spaced therealongfrom said first mounting means;

a first stop member carried by said first mounting means and positionedfor contacting one of said limit switches as said carriage reciprocatesin one direction; and

a second stop member carried by said second mounting means andpositioned for contacting the other of said limit switches as saidcarriage reciprocates in a direction opposite from said one direction.

5. An automatic electric parking brake system as defined in claim landfurther characterized as including a switch mounting bracket secured tosaid trackway and supporting said limit switches in alignment with saidswitch contacting means.

6. An automatic electric parking brake system as defined in claim 1wherein each of said brake actuating elements comprises an elongated,rigid member of C-shaped transverse cross-sectional configuration havingan elongated slot through the bight portion of the C-shaped. crosssection; and wherein said central guide member is an elongated member ofH- shaped cross-sectional configuration defining a pair oflongitudinallyextending grooves slidingly receiving the edge portions ofsaid brakeactuating elements.

7. An automatic electric parking brake system as defined in claim 6wherein said moving means comprises a retainer bolt secured to saidcentral guide member and projecting through the elongated slots in saidautomatic and manual brake actuating elements.

8. An automatic electric parking brake system as defined in claim 1 andfurther characterized to include at least one adjusting link assemblyconnected to said lost motion assembly and between said carriage andsaid flexible means. said adjustable link assembly including:

an L-plate; and

a threaded bolt threaded a pre-adjusted length through said L-plate.

9. An automatic electric parking brake system as defined in claim 8wherein said L-plate has an end connected to said carriage, and whereinsaid system further includes a spring connected to said threaded boltand to said automatic brake actuating element.

10. An automatic electric parking brake system as defined in claim 8wherein said L-plate has an end connected to said central guide member,and said threaded bolt has an end connected to said flexible means.

H. An automatic electric parking brake system as defined in claim 3wherein said carriage comprises:

an elongated base plate having opposed longitudinal edges;

and

antifriction, synthetic resin runners secured to each of said opposedlongitudinal edges and slidingly engaged by said turned over edgeportions of said trackway.

12. An automatic electric parking brake system as defined in claim 11wherein said carriage further includes:

a first U-shaped bracket secured to said base plate adjacent one endthereof;

a second U-shaped bracket secured to said base plate adjacent theopposite end of said base plate from that nearest said first U-shapedbracket;

a first supporting member secured to said first U-shaped bracket andextending outwardly therefrom;

a second supporting member secured to said second U- shaped bracket andextending outwardly therefrom;

a first adjusting screw extending into said first supporting member andpositioned for contacting one of said limit switches as said carriagereciprocates in one direction; and

a second adjusting screw extending into said second supporting memberand positioned for contacting the other of said limit switches as saidcarriage reciprocates in a direction opposite from said one direction.

13. An automatic electric parking brake system as defined in claim 12and further characterized to include a switch mounting bracket securedto said trackway and supporting said limit switches in alignment withsaid adjusting screws.

14. An automatic electric parking brake system as defined in claim 13wherein each of said brake actuating elements comprises an elongated,rigid member of C-shaped transverse cross-sectional configuration havingan elongated slot through the bight portion of the C-shaped crosssection; and wherein said central guide member is an elongated member ofH- shaped cross-sectional configuration defining a pair oflongitudinally extending grooves slidingly receiving longitudinal edgeportions of said brake actuating elements.

15. An automatic electric parking brake system as defined in claim 14wherein said moving means comprises a retainer bolt secured to saidcentral guide member and projecting through the elongated slots in saidautomatic and manual brake actuating elements.

16. An automatic electric parking brake system as defined in claim 15and further characterized to include at least one adjustable linkassembly connected to said lost motion assembly and between saidcarriage and said flexible means, said adjustable link assemblyincluding:

an L-plate; and

a threaded bolt threaded a pre-adjusted distance through said L-plate.

in claim 16 wherein said L-plate has an end connected to said carriage,and wherein said system further includes a spring connected to saidthreaded bolt and to said automatic brake actuating element.

18. An automatic electric parking brake system for an automobilecomprising:

a reversible motor; a trackway adapted for securement to saidautomobile; a carriage slidably mounted in said trackway;

a threaded shaft secured to, and movable with, said carriage; gearingdrivingly engaging said threaded shaft for driving said shaft inrotation; v a housing around said gearing secured to said carriage, and

i said shaft passing through said housing; a flexible drive cabledrivingly connected to said reversible motor and extending into saidhousing and connected to said gearing;

- an adjusting link assembly connected to said carriage;

a flexible brake cable adapted for connection to the brakes of theautomobile; means connecting said brake cable to said adjusting linkassembly; and electrical circuitry including an automobile ignitionswitch connected to said reversible motor and driving said motor in onedirection of rotation for a limited period of time when said ignitionswitch is turned on to close the circuitry, and driving said motor in anopposite direction of

